What indicators that I should check?

Building permits, a leading indicator of future construction activity, were up by 1.5% to 1.80 million units.Rent costs rising over the past few years could finally be hitting the consumer's wallet in that they are becoming weaker and unable to afford higher rents.Also, looking at the housing starts data, new supply may be entering the market finally, causing prices to drop as consumers have more options. 

He indicated he would call the post office soon but had not yet.

I have found that the depreciation expense can be a could indication of the above mentioned “unexpected” expenses. 

Borrowing this kind of money to fund aggressive spend on growth in a high gross margin industry is once thing; covering Op-ex shortfalls is indicative of near term distress. 

US 10 year Treasury yields tumbled (by nearly 10 basis points today and counting..) with the latest inflation metrics showing a dip last month indicating the Federal Reserve could start to lower interest rates this year with a now 80% chance of a September rate cut. 

In his presentation he indicated that buying liens or deeds was as simple as going to their website and just clicking on the property and buy the lien getting a guaranteed 18%- 25% interest return or a property if taxes we not paid.

I do have 5 property managements for my rentals and how they are different is how the process for repair is different from one to another, but i see someone that's more pop and mom is having so much passion about real estate, that passion is kinda my indicator right now.

FWIW, a CPA indicated single entity LLCs don't provide the same level of legal protection as multi-member LLCs provide.

Generally a higher cap rate indicates a lower credit tenant which indicates a higher risk to the property owner. a 10 cap is a great deal until the tenant goes out of business and leaves you with a Negative 10 cap as you are on the hook for all of the expenses associated with ownership.You should consider creditworthiness of the tenant first and foremost.